perimeter of I a. Since the methoxy groups require less space, one methoxy group on each pyrrole ring is almost in the porphyrin plane (i.e. its C-0 bond and the porphyrin are close to coplanar). The deviation of the CH, carbon atoms of these "planar" methoxy groups from the best plane of the porphyrin ring is only 0.415(01) and 2.33(04) A for 1 a, and